The present invention relates to powders of tetrafluoroethylene (TFE) copolymer useful for powder coating, and a process for preparing the same.
Study and development for powders of TFE copolymer used for powder coating have proceeded on the basis of the theory that such powders preferably have a spherical particle shape in a viewpoint of flowability (Japanese Tokkyo Kokai No. 240713/1985).
To roto-molding or roto-lining which has been recently utilized as a method of powder coatings, however, the above theory could not be fully applied. For instance, there are some problems such that a coating formed on a mold surface partially falls off to yield coating defects on a surface of the molded article, that a coating surface largely undulates and has continuous ball-like projections, and that a coating contains bubbles or cells because its gas content cannot be sufficiently removed.
As a result of the inventors' intensive study, it has been found out that the above-mentioned problems can be solved by using powders of TFE copolymer having particular powder properties.